Valve timing adjuster

ABSTRACT

A valve timing adjuster includes a housing and a vane rotor. A hub portion of the vane rotor includes an advance passage and a retard passage. One of a shoe of the housing and the hub portion includes an advance groove and a retard groove. The advance groove provides communication between an advance chamber and the advance passage at a full retard position. The retard groove provides communication between a retard chamber and the retard passage at a full advance position. The advance groove and the retard groove are spaced apart from each other along a longitudinal axis of the housing.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2010-37086 filed on Feb. 23, 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a valve timing adjuster for an internal combustion engine, which adjuster adjusts timing of opening and closing at least one of an intake valve and an exhaust valve.

2. Description of Related Art

Conventionally, a valve timing adjuster is known to adjust timing of opening and closing at least one of an intake valve and an exhaust valve by changing a phase between a crankshaft and a camshaft. The crankshaft serves as a drive shaft of an internal combustion engine (hereinafter referred to as an engine). The camshaft serves as a driven shaft that opens and closes the intake valve and/or the exhaust valve based on the driving force of the crankthaft.

In general, the valve timing adjuster has a housing and a vane rotor. The housing rotates synchronously with the crankshaft, and receives therein the vane rotor. The vane rotor is rotatable synchronously with the camshaft. The housing has shoes that radially inwardly project from the tubular peripheral wall of the housing, and shoes slides on an outer wall of the vane rotor. Multiple pressure chambers are sectioned by the shoes between an inner wall of the housing and the outer wall of the vane rotor. Also, the vane rotor has multiple vanes that divide the multiple pressure chambers into advance chambers and retard chambers. When pressures of oil supplied to the advance chambers or the retard chambers are applied to pressure receiving surfaces of the multiple vanes, the housing rotates relative to the vane rotor, and thereby the phase between the crankshaft and the camshaft is changed accordingly.

The enlargement of a phase changeable angle of the valve timing adjuster has been demanded in order to address various operational conditions of the engine, and in order to improve the engine performance and the exhaust gas purification capability. Also, in order to improve the easiness of mounting the valve timing adjuster to the engine, the reduction in the size of the valve timing adjuster has been also demanded.

In order to enlarge the phase changeable angle of the valve timing adjuster, the numbers of the pressure chambers and the vanes are reduced, and thereby the dimensions of the remaining pressure chambers are increased in the circumferential direction to increase the volumes thereof. However, the total area of the vanes, which receive oil pressure, is reduced with the reduction of the number of the vanes accordingly, and thereby torque applied to the housing and the vane rotor are reduced accordingly. When the torques are reduced below the reaction force of the camshaft, it becomes difficult to rotate the vane rotor relative to the housing. As a result, the range of the engine rotational speed, in which the valve timing adjuster is effectively phase-controlled, may be limited disadvantageously.

In contrast, in a case where pressure receiving surfaces of the vanes are increased in order to increase torque applied to the housing and the vane rotor, the size of the valve timing adjuster may be increased disadvantageously.

In JP3906482, a valve timing adjuster operates oil pressure higher in the advance control than in the retard control. In the above, oil pressure is supplied to the advance chambers through advance passages, which are formed on a vane rotor. Oil pressure is supplied to the retard chambers through retard passages, which are formed on a rear plate. An angle θ is defined between the advance passage and the retard passage when controlled at the full retard position. An angle φ is defined between the advance passage and the retard passage when controlled at the full advance position. The advance passage and the retard passage are formed such that the angle θ is greater than the angle φ. Thus, leakage (erroneous communication) of oil between the advance chamber and the retard chamber is limited during an advance operation, in which the phase of the vane rotor is advanced from the full retard position.

However, in JP3906482, the advance passage is formed on a longitudinal end surface of the vane rotor to have a curved shape, and the retard passage is formed on the opposed surface of the rear plate that races the end surface of the vane rotor. If the advance passage is formed to have the above curved shape, and simultaneously if the advance passage and the retard passage are separately formed from each other, each passage has to have a complex structure, and thereby man hour of processing the product is disadvantageously increased.

SUMMARY OF THE INVENTION

The present invention is made in view of the above disadvantages. Thus, it is an objective of the present invention to address at least one of the above disadvantages.

To achieve the objective of the present invention, there is provided a valve timing adjuster that adjusts timing of opening and closing at least one of an intake valve and an exhaust valve by changing a phase between a drive shaft of an internal combustion engine and a driven shaft, which opens and closes the at least one of the intake valve and the exhaust valve based on a driving force of the drive shaft. The valve timing adjuster includes a housing and a vane rotor. The housing is rotatable synchronously with one of the drive shaft and the driven shaft. The housing has a tubular peripheral wall, a shoe, a front plate, and a rear plate. The shoe radially inwardly projects from the peripheral wall. The front plate is provided on one side of the peripheral wall along a longitudinal axis of the housing. The rear plate is provided on the other side of the peripheral wall along the longitudinal axis. The vane rotor is rotatable synchronously with the other one of the drive shaft and the driven shaft. The vane rotor includes a hub portion and a vane. The hub portion is provided coaxially with the housing, wherein the hub portion slidably contacts a slidably contacting surface of the shoe located on a radially inner side thereof, wherein the hub portion has a generally hollow cylindrical shape, wherein the peripheral wall, the shoe, and the hub portion defines therebetween a pressure chamber. The vane radially outwardly projects from the hub portion to divide the pressure chamber into an advance chamber and a retard chamber that are arranged in a circumferential direction of the housing. The vane rotor rotates relative to the housing based on pressure of working fluid that is supplied to one of the advance chamber and the retard chamber. The hub portion includes an advance passage and a retard passage. The advance passage has an opening, which faces an advance side of the slidably contacting surface adjacent the advance chamber when the vane rotor is located at a full retard position relative to the housing. The retard passage has an opening, which faces a retard side of the slidably contacting surface adjacent the retard chamber when the vane rotor is located at a full advance position relative to the housing. One of the shoe and the hub portion includes an advance groove and a retard groove. The advance groove provides communication between the advance chamber and the opening of the advance passage when the vane rotor is located at the full retard position relative to the housing. The retard groove provides communication between the retard chamber and the opening of the retard passage when the vane rotor is located at the full advance position relative to the housing. The advance groove and the retard groove are spaced apart from each other along the longitudinal axis of the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a valve timing adjuster according to the first embodiment of the present invention, the view being taken along a line I-I in FIG. 2;

FIG. 2 is a cross-sectional view of the valve timing adjuster taken along a line II-II in FIG. 1;

FIG. 3 is a schematic diagram of a driving force transmission system having the valve timing adjuster according to the first embodiment;

FIG. 4 is a diagram exclusively illustrating a peripheral wall and shoes, of the valve timing adjuster according to the first embodiment

FIG. 5 is a view observed in a direction V in FIG. 4;

FIG. 6 is an enlarged view of a peripheral wall and shoes of a valve timing adjuster according to the second embodiment of the present invention;

FIG. 7 is a cross-sectional view of a valve timing adjuster according to the third embodiment of the present invention, the view being taken along a line VII-VII in FIG. 8;

FIG. 8 is a cross-sectional view of the valve timing adjuster taken along a line VIII-VIII in FIG. 7;

FIG. 9 is a diagram exclusively illustrating a vane rotor of the valve timing adjuster according to the third embodiment;

FIG. 10 is a view observed in a direction X of FIG. 9;

FIG. 11 is an enlarged view of a vane rotor of a valve timing adjuster according to the fourth embodiment of the present invention; and

FIG. 12 is an enlarged view of a peripheral wall and shoes of a valve timing adjuster according to a comparison example.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below with reference to accompanying drawings.

First Embodiment

A valve timing adjuster according to the first embodiment of the present invention is shown in FIGS. 1 to 5.

In a driving force transmission system, as shown in FIG. 3, a gear 3 is fixed to a crankshaft 2 that serves as a drive shaft of an engine 1. Gears 6, 113 are respectively fixed to camshafts 4, 5 that serve as driven shafts. A chain 7 is installed over the gear 3 and the gears 6, 113, and transmits a driving force from the crankshaft 2 to the camshafts 4, 5. The camshaft 4 opens and closes an intake valve 8, and the other camshaft 5 opens and closes an exhaust valve 9. A valve timing adjuster 10 of the present embodiment is a hydraulic control adjuster that employs hydraulic oil as working fluid. The valve timing adjuster 10 adjusts timing of opening and closing the intake valve 8 in a state, where the gear 113 is connected to the chain 7, and where a vane rotor is connected to the camshaft 4.

As shown in FIGS. 1 and 2, the valve timing adjuster 10 has a housing 12 and a vane rotor 20.

The housing 12 includes a tubular peripheral wall 13, four shoes 14 to 17, a front plate 18 and a rear plate 11. The four shoes 14 to 17 radially inwardly projects from the peripheral wall 13. The front plate 18 is provided on one side of the peripheral wall 13 along a longitudinal axis of the housing 12, and the rear plate 11 is provided on the other side of the peripheral wall 13 along the longitudinal axis. In other words, the front plate 18 is provided on one longitudinal side of the peripheral wall 13 in a longitudinal direction of the housing 12, and the rear plate 11 is provided on the other longitudinal side of the peripheral wall 13 opposite from the one longitudinal side.

Each of the shoes 14 to 17 has a generally trapezoidal shape, and the shoes 14 to 17 are provided in a circumferential direction of the peripheral wall 13 of the housing 12 at equal intervals. Four pressure chambers 50 are defined between the adjacent shoes arranged in the circumferential direction.

The front plate 18 has an axial hole 18 a, through which the camshaft 4 extends in the longitudinal direction.

The rear plate 11 has the gear 113 at a position radially outward of the rear plate 11. Also, the rear plate 11 has an axial hole 11 a, through which the camshaft 4 extends in the longitudinal direction. The front plate 18 and the rear plate 11 are rotatable relative to the camshaft 4.

The vane rotor 20 is coaxially received within the housing 12. The vane rotor 20 has a hub portion 21 and four vanes 24 to 27. The hub portion 21 has a generally hollow cylindrical shape, and vanes 24 to 27 radially outwardly project from the hub portion 21.

The hub portion 21 has an axial hole 21 a, through which the camshaft 4 extends in the longitudinal direction. The hub portion 21 is fixed to the camshaft 4 though a method, such as press fitting, welding, or a bolt. Due to the above, the vane rotor 20 is rotatable synchronously with the camshaft 4.

The vanes 24 to 27 divide corresponding pressure chambers 50 into retard chambers 51 to 54 and advance chambers 55 to 58, and the retard chambers 51 to 54 and the advance chambers 55 to 58 are arranged in a circumferential direction of the housing 12.

The hub portion 21 has an outer diameter that is slightly smaller than an inner diameter of the shoes 14 to 17. Therefore, the shoes 14 to 17 have slidably contacting surfaces 41 to 44 at radially inner side thereof, and the slidably contacting surfaces 41 to 44 slidably contact a radially outer wall of the hub portion 21. The above arrangement of the slidably contacting surfaces 41 to 44 of the shoes 14 to 17 and the outer wall of the hub portion 21 limits leakage or circulation of hydraulic oil between (a) the retard chambers 51 to 54, which are formed on one circumferential side of the shoes 14 to 17, and (b) the advance chambers 55 to 58, which are formed on the other circumferential side of the shoes 14 to 17.

Each of the vanes 24 to 27 has an outer diameter that is slightly smaller than an inner diameter of the peripheral wall 13 of the housing 12. Seal members 28 are made of, for example, a resin, and the seal members 28 are fitted into radially outer walls of the vanes 24 to 27. The seal members 28 are pressed against the peripheral wall 13 by resilient force of respective leaf springs (not shown). The seal members 28 limit leakage of hydraulic oil through clearances between (a) the radial outer walls of the vanes 24 to 27 and (b) the peripheral wall 13, and thereby limiting communication of hydraulic oil between (a) the retard chambers 51 to 54 and (b) the advance chambers 55 to 58.

The vane 27 is provided with a hole 29, and the hole 29 is provided with a stopper piston (not shown). The rear plate 11 has a fitting ring, and the stopper piston is fitted into the fitting ring of the rear plate 11 to regulate the relative rotation between the housing 12 and the vane rotor 20. The description of the configuration of the stopper piston is omitted.

The valve timing adjuster 10 of the present embodiment rotates clockwise when observed in a direction indicated by an arrow A in FIG. 2. The above rotational direction is defines as an advance direction.

Arrows labeled as “advance” and “retard” in FIG. 1 indicate an advance direction and a retard direction of the vane rotor 20 relative to the housing 12.

The housing 12 is rotatable relative to the vane rotor 20. In other words, when pressure of oil supplied to each of the retard chambers 51 to 54 is applied to the inner wall the housing 12 and the outer wall of the vane rotor 20, the vane rotor 20 rotates relative to the housing 12 in the retard direction. In contrast, when pressure of oil supplied to the advance chambers 55 to 58 is applied to the inner wall of the housing 12 and the outer wall of the vane rotor 20, the vane rotor 20 rotates relative to the housing 12 in the advance direction. FIG. 1 shows a phase changeable angle 81 of the valve timing adjuster 10. For example, the phase of the vane rotor 20 relative to the housing 12 is changeable within the phase changeable angle θ1.

It should be noted that in FIG. 1, the phase of the vane rotor 20 relative to the housing 12 is controlled such that the vane rotor 20 is positioned at a full advance position.

Next, a supply passage of oil pressure of the valve timing adjuster 10 will be described.

The camshaft 4 and the hub portion 21 define therein retard passages 31 to 34 and advance passages 35 to 38, each of which extends in a radial direction. The retard passages 31 to 34 are formed at positions such that the openings of the retard passages 31 to 34 are located at respective retard sides of the slidably contacting surfaces 41 to 44 adjacent the retard chambers 51 to 54 when the phase of the vane rotor 20 relative to the housing 12 is controlled to the full advance position. In contrast, the advance passages 35 to 38 are formed at positions such that the openings of the advance passages 35 to 38 are located at respective advance sides of the slidably contacting surfaces 41 to 44 adjacent the advance chambers 55 to 58 when the phase of the vane rotor 20 relative to the housing 12 is controlled to the full retard position.

The slidably contacting surfaces 41 to 44 have retard grooves 61 to 64 and advance grooves 65 to 68, respectively. The retard grooves 61 to 64 are formed at positions such that the retard grooves 61 to 64 provide communication between the openings of the retard passages 31 to 34 and the retard chambers 51 to 54 when the phase of the vane rotor 20 relative to the housing 12 is controlled to the full advance position. In contrast, the advance grooves 65 to 68 are formed at positions such that the advance grooves 65 to 68 provide communication between the openings of the advance passages 35 to 38 and the advance chambers 55 to 58 when the phase of the vane rotor 20 relative to the housing 12 is controlled to the full retard position.

The retard groove, the advance groove, and the slidably contacting surface, which is provided with the retard and advance grooves, will be detailed with reference to FIG. 4 and FIG. 5. FIG. 4 shows only the peripheral wall 13 and the shoes 14 to 17 of the valve timing adjuster 10. FIG. 5 is a view observed in a direction V in FIG. 4. In other words, FIG. 5 shows the shoe 14 and a part of the peripheral wall 13 in the vicinity of the shoe 14.

It should be noted that FIG. 5 shows a position of the opening of the retard passage 31 by a dashed line when the phase of the vane rotor 20 relative to the housing 12 is controlled to the full advance position. Also, FIG. 5 shows a position of the opening of the advance passage 35 by another dashed line when the phase of the vane rotor 20 relative to the housing 12 is controlled to the full retard position.

The retard groove 61 is provided to one longitudinal end of the slidably contacting surface 41, and the advance groove 65 is provided the other longitudinal end of the slidably contacting surface 41 opposite from the one longitudinal end. Specifically, the retard groove 61 opens to a wall'surface 181 of the shoe 14 adjacent the front plate 18, and also opens to a wall surface 145 of the shoe 14 adjacent the retard chamber 51. In contrast, the advance groove 65 opens to a wall surface 111 of the shoe 14 adjacent the rear plate 11, and also opens to a wall surface 146 of the shoe 14 adjacent the advance chamber 55. For example, the retard groove 61 and the advance groove 65 are spaced apart from each other in the longitudinal direction of the housing 12. Also, the retard groove 61 and the advance groove 65 are spaced apart from each other in the circumferential direction of the housing 12. Thus, the retard groove 61 and the advance groove 65 are positioned on the slidably contacting surface 41 diagonally with respect to each other. Thus, a distance L2 measured between the retard groove 61 and the advance groove 65 is maximized. Also, because the retard groove 61 and the advance groove 65 are provided to the slidably contacting surface 41 diagonally with each other as above, it is possible to shorten a distance L5 measured between the retard groove 61 and the advance groove 65 in a circumferential direction. Also, it is possible to shorten a distance L1 of the slidably contacting surface 41 in the circumferential direction accordingly. It should be noted that the retard groove 61 may overlap with the advance groove 65 when observed in the longitudinal direction (a direction B in FIG. 5).

A distance L3 is measured between the retard groove 61 and the wall surface 146 of the shoe 14 adjacent the advance chamber 55. A distance L4 is measured between the advance groove 65 and the wall surface 145 of the shoe 14 adjacent the retard chamber 51. The distance L1 is a dimension of the slidably contacting surface 41 in the circumferential direction as above. The distance L2 is diagonally measured between the retard groove 61 and the advance groove 65. All of the distances L1, L2, L3, and L4 are determined such that the sealing performance of the clearance between the slidably contacting surface 41 and the outer wall of the hub portion 21 is substantially achievable. Due to the above configuration, the leakage (erroneous communication) of hydraulic oil between (a) the retard chamber 51 formed on one circumferential side of the shoe 14 and (b) the advance chamber 55 formed on the other circumferential side of the shoe 14 is effectively limited.

Next, the operation of the valve timing adjuster 10 will be described.

<During Starting of Engine>

When the engine 1 is not running, the stopper piston is fitted into the fitting ring. Immediately after the engine 1 is started, a hydraulic pump 90 has not sufficiently supplied hydraulic oil to the retard chambers 51 to 54 and the advance chambers 55 to 58. Thus, the stopper piston remains fitted into the fitting ring, and thereby the phase of the camshaft 4 relative to the crankshaft 2 is held at the full retard position. As a result, it is possible to prevent the noise of the collision between the housing 12 and the vane rotor 20 caused by variation of torque applied to the camshaft 4 before hydraulic oil is sufficiently supplied to each pressure chamber 50.

<After Engine Start>

After the engine start, when the hydraulic pump 90 supplies hydraulic oil, the stopper piston moves out of the fitting ring or is disengaged from the fitting ring, and thereby the vane rotor 20 is allowed to rotate relative to the housing 12. Then, by controlling the pressure of oil in the retard chambers 51 to 54 and the advance chambers 55 to 58, it is possible to adjust the phase difference of the camshaft 4 relative to the crankshaft 2.

<During Advance Operation>

When the valve timing adjuster 10 is controlled under the advance operation, an electronic control device (ECU) 91 controls drive electric current supplied to a switching valve 92. As a result, the switching valve 92 connects the hydraulic pump 90 with an advance passage 93, and connects a retard passage 94 with an oil pan 95. Hydraulic oil discharged from the hydraulic pump 90 is delivered through the advance passage 93, 35 to 38 and the advance grooves 65 to 68, and is supplied to the advance chambers 55 to 58. In contrast, hydraulic oil in the retard chambers 51 to 54 is delivered through the retard grooves 61 to 64 and the retard passages 31 to 34, 94, and is drained to the oil pan 95. Oil pressure in the advance chambers 55 to 58 is applied to the housing 12 and to the vanes 24 to 27, and generates a torque that urges the vane rotor 20 in the advance direction. Thus, the vane rotor 20 rotates relative to the housing 12 in the advance direction.

<During Retard Operation>

When the valve timing adjuster 10 is controlled under the retard operation, the ECU 91 controls drive electric current supplied to the switching valve 92. Thus, the switching valve 92 connects the hydraulic pump 90 with the retard passage 94, and connects the advance passage 93 with the oil pan 95. Hydraulic oil discharged from the hydraulic pump 90 is delivered through the retard passage 94, 31 to 34 and the retard grooves 61 to 64, and is supplied to the retard chambers 51 to 54. In contrast, hydraulic oil the advance chambers 55 to 58 is delivered through the advance passages 35 to 38, 93 and the advance grooves 65 to 68, and is drained to the oil pan 95. Oil pressure in the retard chambers 51 to 54 is applied to the housing 12 and the vanes 24 to 27, and generates a torque that urges the vane rotor 20 in the retard direction. As a result, the vane rotor 20 rotates relative to the housing 12 in the retard direction.

<Holding at Intermediate Position>

When the vane rotor 20 reaches a target phase, the ECU 91 controls a duty ratio of the drive electric current supplied to the switching valve 92. Then, the switching valve 92 disconnects the hydraulic pump 90 from the retard passage 94 and also disconnects the hydraulic pump 90 from the advance passage 93. Thus, discharge of hydraulic oil from the retard chambers 51 to 54 and the advance chambers 55 to 58 to the oil pan 95 is prevented. Thus, the vane rotor 20 is held at the target phase.

<During Stopping Engine>

When a command of stopping the engine 1 is issued during the operation of the valve timing adjuster 10, the vane rotor 20 is rotated relative to the housing 12 in the retard direction in a manner similar to the retard operation, and the rotation of the vane rotor 20 is stopped at the full retard position. In the above state, the ECU 91 stops the operation of the hydraulic pump 90, and causes the switching valve 92 to connect the retard passage 94 with the oil pan 95. Due to the above operation, the stopper piston is brought into fitting with the fitting ring.

Comparison Example

FIG. 12 shows an enlarged view of a peripheral wall and a shoe of a valve timing adjuster according to the comparison example. It should be noted that similar components of the comparison example and multiple later-described embodiments, which are similar to the components of the first embodiment will be indicated by the same numerals, and the description will be omitted.

In the comparion example, a retard groove 611 and an advance groove 651 are formed on the slidably contacting surface 411 to extend over the length of the slidably contacting surface 411 in the longitudinal direction. In other words, the retard groove 611 and the advance groove 651 are formed from (a) the end surface 181 of the slidably contacting surface 411 adjacent the front plate to the other end surface 111 of the slidably contacting surface 411 adjacent the rear plate. In FIG. 12, in order to clearly describe the positions of the retard groove 611 and the advance groove 651, the positions of the retard groove 611 and the advance groove 651 are shaded by diagonal lines.

In the comparison example, a distance L9 measured between the retard groove 611 and the advance groove 651 is determined such that the sealing performance is substantially achievable. As a result, a distance L10 of the shoe 141 in the circumferential direction measured as shown in FIG. 12 is made longer than the distance L1 of the shoe 14 in the circumferential direction according to the first embodiment.

Advantages of First Embodiment

In the first embodiment, the retard grooves 61 to 64 and the advance grooves 65 to 68 are provided to the slidably contacting surfaces 41 to 44 diagonally with respect to each other. When the distance L2 measured between the retard grooves 61 to 64 and the advance grooves 65 to 68 is maximized as above, it is possible to enlarge the sealing area, and thereby improving the sealing performance (or sealing capability) of limiting hydraulic oil from leaking through the clearance between the slidably contacting surfaces 41 to 44 and the outer wall of the hub portion 21.

In the valve timing adjuster 10 of the first embodiment, the retard groove 61 and the advance groove 65 are provided to the slidably contacting surface 41 at positions diagonally with each other as described above. Thus, even when the sealing performance in the first embodiment is equivalent to the sealing performance in the comparison example, or in other words, even when the distance L9 in the comparison example is generally equivalent to any one of the distances L2, L3, L4 in the first embodiment, it is possible to reduce the distance L5 of the first embodiment, and thereby reducing the distance L1 of the first embodiment. As a result, it is possible to enlarge the dimension of the pressure chambers 50 in the circumferential direction by an amount equivalent to the seduction in the distance L1 or in the distance L5. Therefore, it is possible to increase the phase changeable angle θ1 effectively.

Also, for example, if the distance L1 of the shoe 14 in the circumferential direction is reduced, and simultaneously the outer diameters the housing 12 and the vane rotor 20 are reduced in a state, where the phase changeable angle 01 of the first embodiment remains unchanged, it is possible to reduce the size of the valve timing adjuster in the radial direction.

Furthermore, for example, if the distance L2 of the first embodiment is reduced as much as possible within a range that achieves the substantial sealing performance of hydraulic oil between the slidably contacting surface 41 and the outer wall of the hub portion 21, it is possible to reduce the size of the valve timing adjuster in the longitudinal direction.

Also, for example, even in a condition, where the phase changeable angle θ1 of the first embodiment remains unchanged and the size of the valve timing adjuster remains unchanged, it is possible to increase the torque of the valve timing adjuster through increasing the number of vanes by an amount correspondingly to an amount, by which the dimension of the shoe 14 in the circumferential direction is reduced.

In the present embodiment, both of the advance passages and the retard passages are provided to the vane rotor 20, and accordingly, all the supply passages are intensively formed on one component (or vane rotor). As a result, the configurations of the supply passages are effectively simplified, and thereby the man hour of machining or processing the component is effectively reduced. Also, because the supply passages are not provided to the rear plate, but to the vane rotor, it is possible to limit the leakage of working fluid from the supply passages to the advance chambers or to the retard chambers through the clearance between the vane rotor and the rear plate.

Second Embodiment

FIG. 6 shows only a shoe and a part of the peripheral wall around the shoe of a valve timing adjuster according to the second embodiment of the present invention. The second embodiment is a modification of the first embodiment.

In the present embodiment, the retard groove 610 and the advance groove 650 are provided to the slidably contacting surface 41 to extend in the circumferential direction but not in the longitudinal direction. Specifically, the retard groove 610 does not open to the wall surface 181 of the shoe 14 adjacent the front plate 18. However, the retard groove 610 opens only to the wall surface 145 of the shoe 14 adjacent the retard chamber 51. Also, the advance groove 65 does not open to the wall surface 111 of the shoe 14 adjacent the rear plate 11. However, the advance groove 65 opens only to the wall surface 146 of the shoe 14 adjacent the advance chamber 55.

In the present embodiment, the retard groove 610 and the advance groove 650 may be relatively easily formed by cutting off the slidably contacting surface 41 in the circumferential direction through a method, such as milling. By forming the retard groove 610 and the advance groove 650 as above, it is possible to reduce the man hour of the processing the product.

Third Embodiment

A valve timing adjuster 103 according to the third embodiment of the present invention is shown in FIGS. 7 to 10. In the present embodiment, retard grooves 71 to 74 and advance grooves 75 to 78 are formed at the outer wall of the hub portion 21.

FIG. 9 shows only the vane rotor 20 of the valve timing adjuster 103, and FIG. 10 shows a view of the vane rotor 20 observed in a direction X in FIG. 9. FIG. 10 shows two vanes 25, 26 and a part of the outer wall the hub portion 21 around the vanes 25, 26.

It should be noted that in FIG. 10, positions of both ends 431, 432 of the slidably contacting surface 43 of the shoe 16 are indicated by dashed lines when the phase of the vane rotor 20 relative to the housing 12 is controlled to the full advance position.

A retard groove 73 is provided on one longitudinal side of the outer wall of the hub portion 21, and an advance groove 77 is provided on the other longitudinal side of the outer wall of the hub portion 21 opposite from the one longitudinal side. Specifically, the retard groove 73 opens to a wall surface 182 of the hub portion 21 adjacent the front plate 18, and extends to a boundary line 250 between the hub portion 21 and the vane 25. The advance groove 77 opens to a wall surface 112 of the hub portion 21 adjacent the rear plate 11, and extends to a boundary line 260 between the hub portion 21 and the other vane 26. As above, the retard groove 73 and the advance groove 77 are provided at the outer wall of the hub portion 21 diagonally relative to each other.

Another comparison example will be described. In the comparison example, the retard groove and the advance groove are provided to the hub portion to extend over a length of the hub portion in the longitudinal direction. Thus, the retard groove and the advance groove are formed to extend from the front plate side to the rear plate side. The above configuration shortens a distance, which is measured between the retard groove and the end portion of the slidably contacting surface of the shoe in the circumferential direction when the phase is controlled to the full advance position. As a result, the area of the slidably contacting surface becomes smaller, and thereby the sealing performance deteriorates. Thereby, a distance L7, which is diagonally measured between the retard groove 73 and an end portion 432 of the slidably contacting surface 43, of the valve timing adjuster 103 according to the third embodiment is longer than the above circumferential distance of the comparison example. Due to the above configuration, it is possible to increase the area of the slidably contacting surface 43, and thereby it is possible to limit the leakage of hydraulic oil between (a) the retard chamber 53, which is defined between the vane 25 and the shoe 16, and (b) the advance chamber 57, which is defined between the vane 26 and the shoe 16.

In the present embodiment, the retard grooves 71 to 74 and the advance grooves 75 to 78 are diagonally provided relative to each other at positions on the outer wall of the hub portion 21 between the vanes 14 to 17. As a result, the sealing performance between the slidably contacting surfaces 41 to 44 and the outer wall of the hub portion 21 is effectively improved. Furthermore, in the valve timing adjuster 10 of the present embodiment 3, the distance L7, which is diagonally measured between the retard groove 73 and the end portion 432 of the slidably contacting surface 43, is made longer than the distance L2, which is diagonally measured between the retard groove 61 and the advance groove 65 in the first embodiment. As a result, in the valve timing adjuster 10 of the present embodiment 3, it is possible to furthermore improve the sealing performance between the slidably contacting surfaces 41 to 44 and the outer wall of the hub portion 21 compared with the first embodiment. Thereby, it is possible to effectively enlarge the phase changeable angle, and effectively reduce the size of the valve timing adjuster.

Fourth Embodiment

FIG. 11 shows only a vane rotor of a valve timing adjuster according to the fourth embodiment of the present invention. The fourth embodiment is a modification of the third embodiment.

In the present embodiment, a retard groove 730 and an advance groove 770 are formed on the outer wall of the hub portion 21 to extend in the circumferential direction instead of in the longitudinal direction. More specifically, the retard groove 730 extends to a position near the boundary line 250 between the hub portion 21 and the vane 25. Also, the retard groove 730 does not open to the wall surface 182 of the hub portion 21 adjacent the front plate 18. Similarly, the advance groove 770 extends to a position near the boundary line 260 between the hub portion 21 and the vane 26. Also, the advance groove 770 does not open to the wall surface 112 of the hub portion 21 adjacent the rear plate 11.

In the present embodiment, the retard groove 730 and the advance groove 770 may be formed by cutting off the outer wall of the hub portion 21 in the circumferential direction through a method, such as milling. By forming the retard groove 730 and the advance groove 770 as above, the man hour of processing the product is effectively reduced.

Other Embodiment

In the above embodiments, the valve timing adjuster controls the intake valve of the internal combustion engine. However, the present invention may be applicable to a valve timing adjuster that controls an exhaust valve of the internal combustion engine.

In the above embodiments, the front plate 18 and the rear plate 11 are formed separately from the peripheral wall 13 of the housing 12 and from the shoes 14 to 17. However, in another embodiment of the present invention, the peripheral wall, the shoes, the front plate, and the rear plate are all integrated with each other.

Also, in the above embodiments, the gear 113 is provided to the rear plate 11 at a position radially outward of the rear plate 11. However, in another embodiment of the present invention, the gear may be provided at a position radially outward of the peripheral wall of the housing or of the front plate.

As above, the present invention is not limited to the above embodiments, and thereby the present invention may be modified in various manners provided that the modification does not deviate from gist and the scope of the present invention.

Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. 

1. A valve timing adjuster for adjusting timing of opening and closing at least one of an intake valve and an exhaust valve by changing a phase between a drive shaft of an internal combustion engine and a driven shaft, which opens and closes the at least one of the intake valve and the exhaust valve based on a driving force of the drive shaft, the valve timing adjuster comprising: a housing that is rotatable synchronously with one of the drive shaft and the driven shaft, wherein the housing having: a tubular peripheral wall; a shoe that radially inwardly projects from the peripheral wall; a front plate that is provided on one side of the peripheral wall along a longitudinal axis of the housing; and a rear plate that is provided on the other side of the peripheral wall along the longitudinal axis; and a vane rotor that is rotatable synchronously with the other one of the drive shaft and the driven shaft, wherein: the vane rotor includes: a hub portion that is provided coaxially with the housing, wherein the hub portion slidably contacts a slidably contacting surface of the shoe located on a radially inner side thereof, wherein the hub portion has a generally hollow cylindrical shape, wherein the peripheral wall, the shoe, and the hub portion defines therebetween a pressure chamber; and a vane that radially outwardly projects from the hub portion to divide the pressure chamber into an advance chamber and a retard chamber that are arranged in a circumferential direction of the housing; the vane rotor rotates relative to the housing based on pressure of working fluid that is supplied to one of the advance chamber and the retard chamber; the hub portion includes: an advance passage that has an opening, which faces an advance side of the slidably contacting surface adjacent the advance chamber when the vane rotor is located at a full retard position relative to the housing; and a retard passage that has an opening, which faces a retard side of the slidably contacting surface adjacent the retard chamber when the vane rotor is located at a full advance position relative to the housing; one of the shoe and the hub portion includes: an advance groove that provides communication between the advance chamber and the opening of the advance passage when the vane rotor is located at the full retard position relative to the housing; and a retard groove that provides communication between the retard chamber and the opening of the retard passage when the vane rotor is located at the full advance position relative to the housing; and the advance groove and the retard groove are spaced apart from each other along the longitudinal axis of the housing.
 2. The valve timing adjuster according to claim 1, wherein: the one of the shoe and the hub portion is the shoe; the advance groove and the retard groove are formed on the slidably contacting surface of the shoe; one of the advance groove and the retard groove is provided on a side of the slidably contacting surface adjacent the rear plate; and the other one of the advance groove and the retard groove is provided on the other side of the slidably contacting surface adjacent the front plate.
 3. The valve timing adjuster according to claim 2, wherein: the advance groove and the retard groove extend in the circumferential direction without extending along the longitudinal axis.
 4. The valve timing adjuster according to claim 1, wherein: the one of the shoe and the hub portion is the hub portion; the advance groove and the retard groove are formed on an outer wall of the hub portion; one of the advance groove and the retard groove is provided on a side of the outer wall of the hub portion adjacent the rear plate; and the other one of the advance groove and the retard groove is provided on the other side of the outer wall of the hub portion adjacent the front plate.
 5. The valve timing adjuster according to claim 4, wherein: the advance groove and the retard groove extend in the circumferential direction without extending along the longitudinal axis. 